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If the centre… (Class 12 Physics SQP 2024-25, Q22II)

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PhysicsCBSE Class 12 · Sample paper, session 2024-25 · 3 marks · Short answer

CBSE Class 12 Physics sample paper 2024-25: question 22(II)

From the official CBSE sample question paper for 2024-25, section C, question 22(II), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q22(II) · 3 marks · Short answerSemiconductor Electronics: Materials, Devices and Simple Circuits

If the centre tapping is shifted towards Diode D1 as shown in the diagram, draw the output waveform of the given circuit.

Figure in the paper: Full-wave rectifier with centre-tap transformer; secondary ends A and B connect through diodes D1 and D2 to a common point X of load resistor R_L; centre tap connected to ground and the other end Y of R_L; output across R_L. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

Open one hint at a time and try again before the next.

Hint 1

The emf across each half of the secondary is proportional to its number of turns.

Hint 2

Which diode is connected to the half with fewer turns, and when does it conduct?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Shifting the centre tap towards D1 gives the half of the secondary feeding D1 (A to centre tap) fewer turns than the half feeding D2 (centre tap to B). So the emf across the D1 half is smaller than the emf across the D2 half.

    1 mark

  2. In one half cycle D1 is forward biased and conducts. The current through is from X to Y, and the output is a half-sine hump of smaller peak. In the next half cycle D2 conducts, the current through is in the same direction, and the hump has a larger peak.

    1 mark

  3. Output waveform: still full-wave (both humps on the same side of the time axis, no gaps), but alternate humps have unequal heights: small, large, small, large, …

    1 mark

Answer: Full-wave rectified output with alternate half-cycle humps of unequal amplitude (smaller when D1 conducts, larger when D2 conducts)

Where the marks are

  • Explains unequal emf in the two halves of the secondary (1 mark)
  • Both diodes conduct in alternate half cycles, with current in the same direction through (1 mark)
  • Draws/describes the output with alternately smaller and larger humps (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Semiconductor Electronics: Materials, Devices and Simple Circuits, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2024-25: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.